Talk:Coupling constant

Running Coupling Error

Shouldn't the statement of uncertainty in E times uncertainty in t be greater or equal to hbar DIVIDED by 2? 128.171.31.11 (talk) 09:06, 25 March 2008 (UTC)

Symbol

"coupling constant, usually denoted g"

I think it is $\alpha$ ? — Preceding unsigned comment added by 213.250.12.110 (talk • contribs) 15:18, 27 April 2006

As mentioned in the article, α is proportional to g². Since QED interactions involving fermions-in and fermions-out involve two factors of the coupling constant, they go in orders of α; however, the coupling constant is g. -- Xerxes 20:45, 27 April 2006 (UTC)

What is QCD?

The acronym should be expanded. It kinda pops up in the text. — Preceding unsigned comment added by 134.130.4.46 (talk • contribs) 12:06, 30 April 2006 (UTC)

Its a Yang-Mills theory of strong Interactions which governs the dynamics of quarks, anti-quarks and gluons under the frame work of SU(3) color gauge theory. — Preceding unsigned comment added by M. Yousuf Jamal (talk • contribs) 12:55, 31 October 2017 (UTC)

It's quantum chromodynamics. Alfa-ketosav (talk) 18:15, 6 April 2021 (UTC)

Hierarchy of coupling constants

In the second paragraph, it's said that the gravitational coupling is more important than the magnetic coupling in a large lump of magnetized iron. This statement is misleading. Firstly, a "coupling constant" couples at least two things. So one has to say what this piece of metal is being coupled to. For instance, if we couple it to the Earth then the statement is correct; gravity is more important. But if we couple it to an unmagnetized piece of metal of approximately the same size then the magnetization will be more important.

It might be better to illustrate this with something more fundamental. Consider the forces between two electrons: they are attracted gravitationally but this is overcome by their electric charges. This is because the charge-to-mass ratio is large. On the other hand, the Earth and the Moon interact purely gravitationally since they both have very small charge-to-mass ratios.

Then one can go onto the more technical discussion. Joshua Davis 23:38, 22 September 2006 (UTC)

Gauge coupling

This should be understood to be similar to a dimensionless version of the electric charge defined as

${\sqrt {4\pi \varepsilon _{0}\alpha }}.$

==> But this term is not dimensionless!

Given the fine strcucture constant

$\alpha ={\frac {e^{2}}{4\pi \varepsilon _{0}\hbar c}}$

we yield

$e={\sqrt {4\pi \varepsilon _{0}\hbar c\alpha }}$

Comparing with the Planck charge

$q_{\rm {P}}={\sqrt {\hbar c4\pi \epsilon _{0}}}$

we have

${\frac {e}{q_{\rm {P}}}}={\sqrt {\alpha }}$ ≈ ${\sqrt {137}}$

What was this meant to be? --ErnstS 15:05, 03 Feb. 2009 (CET) —Preceding undated comment was added at 14:02, 3 February 2009 (UTC).

energy scale

The article currently contains: “Such processes renormalize the coupling and make it dependent on the energy scale, at which one observes the coupling.”

Someone please add an explanation of the verbal phrase “to observe a coupling at an energy scale ”.

How does one observe a coupling at an energy scale?

The noun “energy ” in this phrase does refer to the energy of which system or object?

87.160.189.219 (talk) 08:58, 8 April 2013 (UTC)

College-Level Layperson Summaries at top of Physics Wiki Pages

This is a general comment & question for those who are active on Wiki Physics articles. Hope I'm posting this in an appropriate place but this article gave me the idea. Disclaimer: I am not a scientist, I'm a nerdy musician.

If I understand this right, the first two paragraphs indicate that a coupling constant is useful in comparing the magnitude of various simultaneous forces affecting an object, when the terms cannot be exactly calculated due to infinities or limits that arise. Due to my uncertainty, I don't feel capable of writing an intro for this article, but

I feel this article would benefit from a 50,000 foot overview to orient the reader.

I realize these pages are designed for scientists, but one of the most brilliant things about Stephen Hawking is that he brought science to non-scientists.

What if every article had a Brief History of Time style intro section? Or something like the 70s National Geographic hardbound books Our World and Our Universe?

Outreach is important--you have an opportunity to interest people in Physics, hook them. It's cool stuff, really it's kind of like magic to be able to hack our universe and learn what makes it tick. If a genius 3rd grader reads these articles and you help that child, you might advance a future scientist who can carry us further by standing on your shoulders. Outreach could also indirectly impact government and corporate funding for hard science by increasing the general public's understanding of science.

Anyway, had to share, sorry if I trolled, feel free to delete this once it's duly-noted, and have a nice day.  :)

D0s4d1 (talk) 09:03, 9 December 2013 (UTC)

Wow, those are beautiful words, and right up there with WP:MTAU. I really would like it if these QM articles would be a bit more understandable in non-scientific terms, but I don't really know how to start doing that, espeially figuring QM has so much advanced basis mathematics (e.g. symmetry groups, which I still don't quite understand). I really hope someone (maybe even my future self? Who knows...) will be able to accomplish that someday soon. 12:12, 12 January 2023 (UTC) UnbiasedBrigade (talk) 12:12, 12 January 2023 (UTC)

1000% agree - I came to this article from a pop science article talking about research suggesting the age of the universe is different than we thought, and the change replies on Tired Light and covering couple constants. I don't plan to do the math. I've got a degree in math, and I still don't want to. Odoketa (talk) — Preceding undated comment added 19:53, 16 March 2024 (UTC)

Wrong labels in running couplings' image

The image with the graph of the dependence of the three (four) coupling constants on the energy scale is wrong. The labels of alpha(em) and alpha(w) are inverted.

193.206.246.25 (talk) 16:38, 10 September 2018 (UTC)

The blue curve (for alpha(em), currently labelled alpha(w)) suggests it approaches an asymptotic value. It, therefore, contradicts the article which states that the QED coupling goes to infinity at the Landau pole.

178.85.217.214 (talk) 21:03, 9 October 2019 (UTC)

Agreed. Replace. BunkCuzkatzimhut (talk) 22:55, 9 October 2019 (UTC)

MS

Why is QCD scale, called $\Lambda _{MS}$, what is 'MS?--ReyHahn (talk) 14:16, 24 June 2020 (UTC)

Minimal subtraction schemeCuzkatzimhut (talk) 14:25, 24 June 2020 (UTC)